1. Field of the Invention
The present invention relates to a novel strain of Xylogone ganodermophthora having antifungal activity against various pathogenic fungi. The above Xylogone ganodermophthora is a novel species identified by the present inventors. The present invention also relates to a composition for controlling plant diseases, particularly Phytophthora capsici, which comprises the above strain, a preparation method thereof and a method for controlling plant diseases using the same.
2. Description of the Prior Art
The control of plant diseases have been mainly based on the wide use of noxious chemicals (agricultural chemicals). Control methods based on such organic synthetic agricultural chemicals cause problems of residual toxicity in crops and soil, because not only target plants and products of the plants, but also soil are frequently treated with noxious chemical substances. It is known that, among these chemicals, many compounds are toxic to microorganisms and animals in addition to target organisms and can also be harmful to humans. Thus, significant portions of recent studies on the control of plant diseases aims to find environment-friendly methods for controlling plant diseases, and one thereof is the development of biological agricultural chemicals based on biological resources antagonist against plant pathogenic microorganisms. As used herein, the term “antagonist microorganisms” refers to microorganisms that inhibit the growth of other kinds of microorganisms when they are cultured with the other microorganisms. The antagonist microorganisms are known to have parasitic, phagocytic and antibiotic activities, etc. Examples of antagonist microorganisms having antifungal activity against pathogenic fungi include Bacillus subtilis var amyloliquefaciens KL1114 (accession No: KCTC 8913P) disclosed in Korean Patent Registration No. 10-0325634, Streptomyces spp. WYE 20 (KCTC 8768P) and WYE 324 (KCTC 8769P) disclosed in Korean Patent Registration No. 10-0197077, and improved Promicromonospora sp. KH-28 KCTC8946P) disclosed in Korean Patent Registration No. 10-0333039.
Under such circumstances, the present inventors isolated and identified Xylogone sphaerospora causing Norang diseases in Ganoderma lucidum. During these isolation and identification procedures, the present inventors have discovered a novel strain showing antifungal activity against various pathogenic fungi, and particularly, have found that an organic solvent extract of a culture of this strain has an antifungal activity against Phytophthora capsici, thereby completing the present invention.
Phytophthora capsici has been classified as belonging to the class Oomycetes of the subdivision Mastigomycotina, but has recently been classified as plant pathogenic fungi belonging to the Chromista group. Phytophthora capsici forms zoospores and spreads from diseased plants to healthy plants through irrigation water and the like. Phytophthora blight that occurred at roots progresses along stems, but in fields in which Phytophthora blight severely occurred, infection of pepper fruits or leaves sometimes occurs directly from soil. In the winter season, Phytophthora capsici forms macrospora, passes the winter and acts as a primary infectious source in the next year. Phytophthora blight occurs mainly in repeated-cultivation farms and spreads rapidly in the rainy season to cause wide economic damage. In addition, it also occurs on seedlings, and due to recent climate warming, it also occurs within one month after planting. In farms which are damaged by the habitual occurrence of Phytophthora blight, the control of Phytophthora blight is performed by methods, including crop rotation, chemical control based on organic synthetic agricultural chemicals, or cultivation of Phytophthora blight resistant varieties. As a cultural method for controlling Phytophthora blight, crop rotation is performed, but when an external to infectious source is introduced, great damage will be caused if chemical control based on synthetic agricultural chemicals is not performed timely. In farms in which Phytophthora blight habitually occurs but crop rotation cannot be performed, the use of Phytophthora blight-resistant varieties can be an effective control method, but the seeds of the varieties are costly, and when a resistant strain appears, it can cause great damage. Thus, the control of Phytophthora blight by synthetic agricultural chemicals is actually difficult to exclude. In current farms, the control of Phytophthora blight by synthetic agricultural chemicals is generally performed, but damage such as the disturbance of the agroecosystem caused by the improper use of synthetic agricultural chemicals is increasing. Accordingly, as a part of an environment-friendly agricultural policy for reducing the use of synthetic agricultural chemicals, biological agricultural chemicals, including microbial agricultural chemicals and biochemical chemicals, are emerging as an alternative to the synthetic agricultural chemicals.